1. Field of the Invention
This invention relates to rotors and is particularly concerned with roots having an axis of rotation and a plurality of radially extending rotor blades rotating in a plane of rotation which can be tilted in any direction relative the axis of rotation. Such rotors are sometimes known as gimbal rotors and can be used in conventional helicopters as either a main sustaining rotor or an anti-torque rotor, and as the sustaining rotor/propeller in tilt wing or tile rotor VTOL aircraft.
2. Description of the Prior Art
EP-A-0221372 describes a constant velocity joint suitable for use in such rotors and comprising six elastomeric bearing assemblies located concentrically around an axis of rotation and with their axes parallel to the axis of rotation. Each elastomeric bearing assembly comprises concentrically arranged cylindrical and spherical elastomeric bearing portions and this may cause difficulty in obtaining optimum properties in all planes of operation and may require large bearings that may be impractical in an operational configuration.
U.S. Pat. No. 4,804,352 describes a link type coupling which can be used for connecting a drive shaft to a rotor hub in an aircraft and having a plurality of links arranged tangentially with respect to driving and driven members and connected thereto by spherical elastomeric bearings at each end. Each link is attached to the driving member through a stub shaft extending generally tangentially of the driving member. In such an arrangement, all of the highly complex movements necessary to permit tilting of the rotor head in any direction relative the axis of rotation must be accommodated in the individual spherical bearings which must also accommodate all of the torque loads.
The present invention aims to overcome the problems of the prior art arrangements.